Bump acorn-walk from 6.1.1 to 7.0.0 (#337)

Bumps [acorn-walk](https://github.com/acornjs/acorn) from 6.1.1 to 7.0.0.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](acornjs/acorn@6.1.1...7.0.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package.json

@@ -9,7 +9,7 @@
   "dependencies": {
     "@types/estree": "0.0.39",
     "acorn": "^6.0.5",
-    "acorn-walk": "^6.1.1",
+    "acorn-walk": "^7.0.0",
     "astring": "^1.3.1",
     "source-map": "^0.7.3"
   },

yarn.lock

@@ -101,9 +101,10 @@ acorn-globals@^4.1.0:
   dependencies:
     acorn "^5.0.0"
 
-acorn-walk@^6.1.1:
-  version "6.1.1"
-  resolved "https://registry.yarnpkg.com/acorn-walk/-/acorn-walk-6.1.1.tgz#d363b66f5fac5f018ff9c3a1e7b6f8e310cc3913"
+acorn-walk@^7.0.0:
+  version "7.0.0"
+  resolved "https://registry.yarnpkg.com/acorn-walk/-/acorn-walk-7.0.0.tgz#c8ba6f0f1aac4b0a9e32d1f0af12be769528f36b"
+  integrity sha512-7Bv1We7ZGuU79zZbb6rRqcpxo3OY+zrdtloZWoyD8fmGX+FeXRjE+iuGkZjSXLVovLzrsvMGMy0EkwA0E0umxg==
 
 acorn@^5.0.0, acorn@^5.3.0:
   version "5.7.1"